Doesn’t differentiate, but my guess would be mostly selling their family home to Blackrock and buying something smaller

56 is all home purchases. the average age of first-time buyers is 38, and of repeat buyers is 61:

The median first-time buyer age increased to 38 years old this year from 35 last year, while the typical repeat buyer age also increased to 61 years from 58 last year.

you can find the full report here (linked in article)

https://www.nar.realtor/research-and-statistics/research-reports/highlights-from-the-profile-of-home-buyers-and-sellers